In a conventional device, a particulate feeder for feeding a powder flocculant (particulate) is disposed in an upper portion of a dissolving tank, the flocculant is fed downward into the dissolving tank through a discharge chute, and by agitating water in the dissolving tank, the flocculant is dissolved into the water (Patent Document 1).
Due to high humidity and so on in the vicinity of the discharge chute in this type of powder flocculant dissolving device, dew condensation forms easily in the vicinity of the discharge chute. Moreover, water droplets may splash up from the dissolving tank and stick to a lower end portion of the discharge chute such that the flocculant forms lumps that stick to the vicinity of the lower end portion of the discharge chute.
In a device proposed in response to this problem, the discharge chute is provided with a duplex structure, air is fed into a space in the interior of the discharge chute, and the air is ejected from a tip end of the discharge chute. In so doing, dew condensation water is prevented from remaining on the tip end portion of the discharge chute, flocculant raw material is prevented from sticking, and so on (Patent Document 2).